The invention relates generally to improvements in fluid flow control systems and, more particularly, to a valve which is operated in cooperation with an infusion device.
In many cases where a fluid containing medication located in a reservoir is infused into the vascular system of a patient through a fluid conduit and cannula, a volumetric flow control device, such as a peristaltic pump, is used to precisely control the infusion of that fluid. The pump operates on the conduit to control the infusion process so that the prescribed amount of the medication is infused in accordance with the therapy schedule. In the cases of some medications, they are most effective when specific amounts are administered over a certain time period. The administration of a lesser or an excess amount may not achieve the desired therapeutic effect with that medication. Additionally, the administration of an excess amount may have an adverse effect on the patient because of the condition of the patient and the characteristics of the medication. Thus, control over the flow of IV fluid to the patient is a significant concern.
With devices such as peristaltic pumps which mechanically operate on the conduit to control flow, flexible tubing is included in the conduit connecting the fluid container with the cannula. Typically, a separate, manually-operated flow stop device located upstream from the pump is used to prevent the free flow of the fluid through the tubing when the pump is not engaged with the tubing. The flow stop device is manually operated to mechanically pinch off the tubing thereby preventing the flow of fluid.
In operation, the tubing is connected to the reservoir with the manual flow stop open so that air is discharged from the tubing by the flow of fluid through it from the reservoir. The manual flow stop is then engaged to pinch the tubing closed at an upstream position so that no flow can occur. The tubing is properly installed in the pump downstream from the manual flow stop and is coupled to the patient. It is common practice to design peristaltic pumps such that no direct fluid flow path exists through the pump from the fluid reservoir to the patient. The tubing is always occluded by one or another mechanism of the pump at all times. For example, the pumping mechanism may be designed to provide continual occlusion of the tubing. The tubing may be occluded against a pressure plate by at least one of the peristaltic fingers when the pump is placed in its operational configuration. In some cases, such pumps have doors, levers, or other mechanisms which interact with the pumping mechanism to control its engagement with the tubing. For example, when moved in one direction, such a lever causes the pressure plate of a peristaltic mechanism to be moved away from the peristaltic fingers so that the tubing can be installed between the two. By moving the lever in the opposite direction, the pressure plate is moved to engage the tubing with the peristaltic fingers thereby placing the pumping mechanism in its operational configuration whereby at least one finger occludes the tubing.
In one case, an engagement lever controls engagement of the peristaltic mechanism with the tubing as described above; however, an access door is also included with the pump. The access door provides protection for the peristaltic mechanism and other components and must first be opened to either install or remove the tubing. Additionally, a magnetically or otherwise activated switch may be used to determine if the access door is closed and the pump will not operate until the magnetic switch senses closure of the door. In some cases, the door and engagement lever may be coupled together so that movement of the door is separate from movement of the engagement lever; that is, they are separate actions. In other cases, movement of the door may cause movement of the lever.
In other cases, the peristaltic mechanism may be pivotally mounted and movement of a tubing access door causes the peristaltic mechanism to pivot away from a stationary pressure plate so that the tubing can be installed. Closing the door after the tubing has been installed causes the peristaltic mechanism to pivot towards the pressure plate and engage the tubing thereby entering the operational configuration.
After installing the tubing in the pump, engaging the pumping mechanism with the tubing, and closing the access door, the upstream manual flow stop device is released from pinching off the tubing. The pump now provides the control over the flow of fluid in the fluid line and even though not operating, is occluding the tubing to prevent the free flow of the fluid.
The pump may be programmed to administer a predetermined amount of the infusion fluid to the patient over a particular time period and then stop pumping and provide a prompt. This predetermined amount of infusion fluid may be less than the amount of fluid in the fluid reservoir and in such a case, fluid will remain in the tubing and in the reservoir after the pump stops. It is normal practice after infusion is complete for the operator to close the upstream manual flow stop thereby pinching off the tubing before disengaging the pumping mechanism from the tubing. Failure to manually pinch off the tubing before opening the pump may allow the free flow of the remaining fluid into the patient because the pump is no longer occluding the tubing. As discussed above, this free flow of additional fluid would not be in accordance with the therapy schedule. It would be desirable in such infusion arrangements to assure that the flow is shut off before the pump is disengaged.
Prior attempts have been made to automatically engage and disengage a tubing clamp in conjunction with the positioning of the peristaltic mechanism. However, the use of a tubing clamp results in physical deformation of the tubing to achieve occlusion and this occluding deformation may leave a permanent deformation in the tubing depending upon how long the tubing is held in the compressed condition by that clamp and how much compressive force is applied. Additionally, failure to properly design such a clamp may even result in permanent deformation of the tubing. Such a result may occur if the clamp exceeds the mechanical limits of the tubing during operation. Permanent deformation of the tubing can impede the flow of fluid to the pump and compromise the ability to maintain high flow rates. Such a result is undesirable.
Hence, those concerned with the infusion of fluids into patients, and particularly, those concerned with flow control devices such as peristaltic-type pumps, have recognized the need for an improved, relatively simple, more economical, durable, and reliable system for preventing the free flow of fluid through a fluid conduit. Those concerned have also recognized the desirability of providing a flow stop system which is interactive with the pumping mechanism so that engagement of the flow stop occurs to shut off the flow before the pumping mechanism is disengaged from the conduit. The present invention fulfills these needs and others.